1. Field of the Invention
The invention relates to a balloon catheter. More particularly, the invention relates to a reduced size intra-aortic balloon catheter and a method for insertion of same.
2. Description of the Prior Art
Intra-aortic balloon (IAB) catheters are used in patients with left heart failure to augment the pumping action of the heart. The catheters, approximately 1 meter long, have an inflatable and deflatable balloon at the inserted distal end. The catheter is typically inserted into the femoral artery over a guidewire and moved up the descending thoracic aorta until the distal tip of the balloon is positioned just below or distal to the left subclavian artery. The proximal end of the catheter remains outside of the patient""s body. A gas shuttle passageway for inflating and deflating the balloon extends through the catheter and is connected at its proximal end to an external pump. The patient""s central aortic pressure is used to time the balloon and the patient""s ECG may be used to trigger balloon inflation in synchronous counterpulsation to the patient""s heartbeat.
Intra-aortic balloon therapy increases coronary artery perfusion, decreases the workload of the left ventricle, and allows healing of the injured myocardium. Ideally, the balloon should be inflating immediately after the aortic valve closes and deflating just prior to the onset of systole. When properly coordinated, the inflation of the balloon raises the patient""s diastolic pressure, increasing the oxygen supply to the myocardium; and balloon deflation just prior to the onset of systole lowers the patient""s diastolic pressure, reducing myocardial oxygen demand.
Intra-aortic balloon (IAB) catheter therapy is the most widely used method of mechanical cardiac assistance. However, limb ischemia remains to be a complication of the IAB therapy accounting up to 10% incidence rate. Historically, IAB catheters have progressed from being quite large in size (12 Fr or 4 mm) down to the recently introduced 8 Fr (2.67 mm) IAB catheter. The unit of Fr is widely used in medical device industry, a diameter of 3 Fr is approximately equal to 1 mm. The advantages of making an IAB catheter smaller are as follows:
higher blood flow through the limb due to lower restriction from the catheter;
easier hemostasis after IAB removal due to smaller insertion wound;
easier insertion of the catheter into tortuous, stenotic, or diseased arterial vessel tree; and
a lower propensity for kinking.
It is desirable therefore to make an IAB catheter as small as possible without compromising the shuttle gas speed.
Traditionally, IAB catheters have two lumens in the catheter: a gas shuttle lumen and a guidewire lumen. The gas shuttle lumen is substantially fixed in size as it has to be large enough to allow the gas to shuttle back and forth without undue restriction to ensure speedy inflation and deflation of the IAB membrane.
The guidewire lumen serves primarily two functions: to aid in inserting the IAB over a previously placed guidewire, and to monitor blood pressure while the IAB is functioning. Recent discoveries and progress with miniature pressure sensors have made it conceivable to place a small pressure sensor into the tip of the catheter, and to monitor the blood pressure via electrical or fiber optic lines running along the catheter to the outside unit with even greater accuracy and stability then through the guidewire lumen, see U.S. patent application Ser. No. 09/734,755, filed on Dec. 12, 2000, herein incorporated by reference in its entirety. Local telemetry and wireless transmission of blood pressure information from the IAB tip sensor to the outside of the patient is also possible. In any case, the pressure monitoring function of the guidewire lumen may be replaced in the future with a sensor embedded in the IAB tip.
However, insertion of the IAB over a guidewire is still a very desirable feature. Direct attempts to make a smaller IAB catheter without the ability to be inserted over the wire are still in the experimental stage. Therefore, the need exists for a single lumen small profile IAB catheter which is insertable using conventional over-the-guidewire techniques.
Furthermore, the need exists to reduce the size of IAB catheters while maintaining the size of the gas shuttle lumen. IAB catheters are generally designed to be inserted through an introducer sheath. Present day IAB catheters, however, are designed for both types of insertion, through a sheath as well as for optional sheathless insertion. As such, the wall thickness of the catheter and the material chosen have to provide sufficient strength and catheter stiffness to withstand the insertion of the IAB and to support the inflation and deflation of the balloon membrane against the pressures generated by the oncoming waves of blood in the descending aorta. Given the need to maintain the size of the gas shuttle lumen, reduction of the IAB catheter profile becomes a difficult design problem. The present invention involves the use of an extended sheath for use during insertion and pumping which allows for a reduction in the overall size of the IAB catheter while maintaining the size of the gas shuttle lumen.
While the present intra-aortic balloon system may be suitable for the particular purpose employed, or for general use, it is not as suitable for the purposes of the present invention as disclosed hereafter.
Accordingly, it is an object of the invention to produce an IAB catheter allowing for higher blood flow through the limb due to a lower restriction from the catheter.
It is a further object of the invention to produce an IAB catheter allowing for easier hemostasis after removal due to a smaller insertion wound.
It is another object of the invention to produce an IAB catheter which provides for an easier insertion into tortuous, stenotic, or diseased arterial vessel trees.
It is still another object of the invention to produce an IAB catheter having a smaller propensity for kinking.
The invention is a reduced size IAB catheter system comprising an IAB catheter disposed within a tube serving both as an insertion sheath and as a reinforcement tube. The tube is preferably disposed about the entire catheter up to the balloon membrane. The catheter remains disposed within the tube during therapy.
To the accomplishment of the above and related objects the invention may be embodied in the form illustrated in the accompanying drawings. Attention is called to the fact, however, that the drawings are illustrative only. Variations are contemplated as being part of the invention, limited only by the scope of the claims.